Jacking Force Transfer System for Bridges with Prefabricated Deck Units

ABSTRACT

A jacking force transfer method to compress prefabricated deck units and to tension bridge girders. Prefabricated deck units are placed on top of bridge girders. Relative motion between girders and deck units is permitted along the direction of bridge girders while deck units are first installed. Subsequently, an end deck unit is made composite with the girders while jacking brackets are installed on top of the deck unit on the other end of the bridge. Hydraulic jacks react with jacking brackets to introduce a longitudinal compression in prefabricated deck units and, at the same time, a tension in the girders.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.62/704,703, filed May 22, 2020 by the present inventor.

FEDERALLY SPONSORED RESEARCH

Not Applicable

SEQUENCE LISTING OR PROGRAM

Not Applicable

BACKGROUND OF THE INVENTION Field of Invention

This invention relates to the construction of bridges with prefabricateddeck units.

Prior Art

For bridges with prefabricated full-depth concrete deck units, it isimportant to have a pre-compression force in the deck to ensure jointintegrity in the service condition. The inventor has proposed severalconstruction methods to apply compression force in prefabricated decks.U.S. Pat. Nos. 8,316,495 B2 and 7,475,446 B1 utilized post-tensioning toapply the needed deck pre-compression force. U.S. Pat. No. 8,266,751B2proposed three methods to compress deck units with jacks. However,jacking methods presented in U.S. Pat. No. 8,266,751B2 carry someshortcomings, such as the need for extensive modifications to thesupporting girder to accommodate the jacking frame attachment; thejacking frame extending outside the bridge deck limits (which can beimpossible due to geometric limitations); the need for a large dimensionsetback of the bridge deck with time consuming cast-in-place deckclosure after the jacking operation; or the need for a significantamount of work to remove the jacking frames.

The current invention provides a jacking force transfer system tofurther improve bridge construction with prefabricated deck units byminimizing the modification to the supporting girders. This allows allequipment and operations to come within the bridge deck limit; andrequires no cast-in-place deck closure after the jacking operation.

Objects and Advantages

The present invention provides a jacking force transfer method forbridges constructed with prefabricate deck units that:

a. Provides pre-compression across joints between deck units by reactingthe deck with supporting bridge girders via the proposed jackingbracket;b. Conducts deck stressing on top of installed deck units to improvework safety;c. Operates entirely within the limit of bridge deck;d. Requires minimum modifications to the bridge supporting girder anddeck units; ande. Requires no cast-in-place deck closure.

Further objects and advantages will become apparent from considering theensuing description and drawings.

SUMMARY

The present invention proposes practical methods to transfer jackingforce to prefabricated bridge deck units using a novel bracket assembly,which simplifies field operation, improves safety and reducesconstruction schedule.

DRAWINGS Figures

FIG. 1 shows the elevation view of an example bridge used to describethe present invention

FIG. 2 shows the plan view of the example bridge

FIG. 3 shows the plan view of a typical prefabricated deck unit

FIG. 3A shows the section view of a deck unit

FIG. 3B shows the shear connector pocket and haunch detail

FIG. 4 shows the mechanism to apply deck compression force

FIG. 5 shows the layout plan of the jacking panel and jacking brackets

FIG. 6 shows the center section view of the jacking bracket

FIG. 6A shows top view of the jacking bracket

FIG. 6B shows section of the jacking bracket at deck level

REFERENCE NUMERALS

-   11 abutment-   12 centerline of abutment-   14 shear connector-   15 girder-   17 haunch-   18 girder top flange-   19 center line of girder-   21 prefabricated deck unit-   22 pocket for shear connectors-   23 shear keys at match cast face-   24 joint between deck units-   25 typical deck unit-   27 deck jacking unit-   28 deck end anchor unit-   29 advanced grouting of haunch and shear connectors for the deck end    anchor unit-   30 jacking bracket-   32 jack-   33 pocket for jacking bracket-   34 jacking bracket side plate-   35 jacking bracket bottom plate-   36 jacking bracket end bearing plate-   37 shims for jack-   38 bearing plate for deck jacking unit-   39 diaphragm for jacking bracket-   52 girder reaction plate-   53 filler plate for reaction plate-   54 hold-down rod coupler-   55 hold-down rod and nuts-   56 leveling block

DETAILED DESCRIPTION FIGS. 1 Through 6—Preferred Embodiment

A preferred embodiment of the bridge with prefabricated deck units usingthe present invention of the jacking force transfer system isillustrated in FIGS. 1 through 6 in the context of a single span bridge,hereinafter referred to as an “example bridge”. The example bridge hastwo abutments 11. The preferred embodiment of the bridge is comprised ofsteel girders 15 acting as main longitudinal structural members, andprefabricated concrete deck units 21 acting as the bridge deck. A deckunit 21 typically connects to adjacent deck units by match cast epoxyjoints 24.

Girders 15 are placed on and supported by abutments 11. Prefabricateddeck units are placed on top of girders 15, seating on a plurality ofleveling devices that sets deck units 21 at the desired elevation andalso allows for relative longitudinal motion between girders 15 and theprefabricated deck units 21.

Each prefabricated deck unit 21 consists of a plurality of pockets 22,similar to those used in conventional prefabricated deck placement, asshown in FIG. 3. Pockets 22 are provided to allow for mechanicalconnection of deck units 21 to girders 15 by means of shear connectors.Haunches 17 will also be grouted at the same time as the shear connectorpockets 22. In the preferred embodiment, shear connectors 14 are shearstuds welded to the girders 15.

FIG. 3B shows the typical connection detail between deck unit and steelgirders. The shear connector 14 is located within the pocket opening 22.The haunch height can be adjusted to meet the profile of the bridge. Inthe completed structure, grout is filled into the haunch 17 and pocketsfor shear connectors 22 to make deck units 21 composite with the girder15.

FIG. 4 shows the overall mechanism of compressing prefabricated deckunits in the preferred embodiment. The jacking mechanism consists of thefollowing elements: 1) a jacking bracket 30 placed on the left end ofthe deck jacking unit 27, 2) a girder reaction plate 52 which isconnected to the supporting girder 15 near the left end of the girder,3) the right end deck unit 28 which is made composite to the supportinggirder 15 by grouting the haunch and pockets for shear connectors 22, 4)typical prefabricated deck units 25 between both end units which aresupported by girders 15 in the vertical direction and are unrestrainedalong the girder longitudinal direction, and 5) a jack 32 placed insidethe jacking bracket 30.

Before deck jacking is applied; the right end deck unit 28 must be madecomposite to the supporting girder 15. At jacking time, the jack 32 isinflated and the jacking action causes compression in the deck andtension in the girder 15.

FIG. 5 shows the plan view of the deck jacking unit 27 and how thejacking brackets 30 are placed. One jacking bracket 30 and one jack 32are required for one girder line.

FIGS. 6-6B show the details of the proposed jacking force transfermethod on the jacking end. Girder reaction plate 52, which takes thejacking force from the jacking bracket 30 to the girder 15, shall beinstalled in advance in the fabrication shop or on-site before deckunits are placed. The jacking reaction plate 52 can be attached to thegirder with different methods. Typically, it is welded or bolted to thetop flange of the steel girder 18. If concrete girders are used for thebridge, girder reaction plates 52 with shear studs can be cast with thegirders 15.

The jacking bracket 30 is the key component of the proposed jackingforce transfer method. The jacking bracket 30 performs the followingfunctions: 1) housing the jack 32, 2) transferring the force from thejack 32 to the girder reaction plate 52, and 3) resisting theoverturning moment caused by jacking force. The jacking bracket 30consists of: 1) the jacking bracket end bearing plate 36, whichinteracts with the jack 32 directly, 2) a pair of jacking bracket sideplates 34, which forms the frame to resist the overturning moment, 3)the jacking 180 bracket bottom plate 35, which reinforces the jackingbracket side plates 34 and jacking bracket end bearing plate 36 as theyreact with the girder reaction plate 52, 4) hold down rods 55 at the endof the jacking bracket side plate 34, which connect to the girder duringjacking operation, 5) diaphragms for jacking bracket 39, which connectboth jacking bracket side plates 34.

The jacking bracket 30 is installed inside a deck opening in the deckjacking unit 27. The jacking bracket bottom plate 35 sets on the girdertop flange 18. The jacking bracket end bearing plate 36 shall be alignedwith the girder reaction plate 52 in both vertical and transversedirections. In order to transfer the jacking force to the girder, thelower end of the jacking bracket end bearing plate 36 shall engage thegirder reaction plate 52 tightly along the longitudinal direction of thebridge. Filler plates for the reaction plate 53 may be used to fill thegap between the jacking bracket end bearing plate 36 and the girderreaction plate 52. Dimensions in gaps can vary due to constructiontolerance, such as variation in girder position, variation in girderreaction plate placement and variation in deck unit placement.Therefore, filler plates 53 with various lengths, typically in ¼″increment, are prepared for each project. After the deck jacking unit 27is installed, the distance between the pocket for jacking brackets 33and girder reaction plates 52 is measured and a filler plate 53 withappropriate length is installed. The jacking bracket 30 is then placedwith the jacking bracket bottom plate 35 tightly against the fillerplate 53.

The front end of the jacking bracket (point toward the middle of thebridge span) seats on the leveling block 56 with appropriate height sothat the bottom of the jacking bracket side plate 34 is parallel to thedeck. Afterward, hold-down rods and nuts 55 are installed to connect thejacking bracket front end to the girder. Hold-down rods shall besecurely connected to the girder and are capable to take tension invertical direction. Hold-down nuts shall be snuggly tightened only sothat the jacking bracket 30 can have slight movement relative to thedeck jacking unit 27 during jacking. Hold-down rods 55 are used tobalance the overturning moment caused by jacking.

At the jacking time, a jack 32 is placed inside the jacking bracket 30where the center of the jack 32 aligns with center of the deck unit 27in the vertical direction. When the jack 32 is inflated, it pushes thejacking bracket end bearing plate 36 on the back end and the bearingplate embedded in the deck jacking unit 38 on the front end. The jackingforce acting on the back end is transferred into girder tension via thegirder reaction plate 52. The jacking force acting on the deck jackingunit 27 becomes compression across all joints 24 between prefabricateddeck units and is balanced by the girder restraint force from deck endanchor unit 28 at the right end of the bridge. The offset between deckcompression (at deck center) and girder reaction (at girder reactionplate 52) results in an overturning moment acting on the jackingbracket. Such overturning moment causes tension in hold-down rods 55 andcompression between the jacking bracket 30 and the girder top flange 18.

Alternate embodiments for the present invention are describedhereinafter:

The bridge layout can be a single span or multiple spans;The girder 15 can be comprised of any other material or cross-sectionsuitable to support the loads applied to these members such as steelI-girders, precast prestressed concrete beams, composite materialI-girders, single or multiple box girders of steel or concrete, trusses,wood beams, etc.:Though the preferred embodiment of the present invention is presented inthe context of bridges, it is not limited to bridge applications. Anystructural application requiring decking support by longitudinalstructure members can utilize the present invention in alternateembodiments such as building floor systems and building roof systems;Joints 24 between adjacent prefabricated concrete deck units can be ofthe match-cast type, with or without epoxy, or cast-in-place usingconcrete, grout or other suitable jointing materials. In the preferredembodiment, match-cast epoxy joints are used;The preferred embodiment utilizes grouted haunch 17 and shear connectorpockets 22 to restrain relative movement between the deck end anchorunit 28 and the girder 15 before jacking. Such restraint can be providedby other means such as installing steel restraining angles or providinganother set of jacking brackets 30 on for deck end anchor units 28;The preferred embodiment utilizes grout to make deck units compositewith supporting girders 15. Any other materials such as UHPC or othermeans such as bolting or welding to prevent the deck unit from movingrelatively to the girder can be utilized to form such composite action;The preferred embodiment places the deck jacking unit 27 on the left endof the bridge and the deck end anchor unit 28 on the right end of thebridge. The reversed arrangement of the deck jacking unit 27 is alsovalid; andThe preferred embodiment utilizes one jacking bracket 30 per girder line19. The deck compression can be applied without having jacking brackets30 on each girder line 19.

Operation

The construction of the preferred embodiment in the context of theexample bridge is illustrated hereinafter.

Abutments 11 are constructed. Girders 15 are erected. Prefabricated deckunits 21 are erected, placing one unit adjacent to the previouslyerected one and applying epoxy to the adjacent faces of the two deckunits. Means will be employed to provide a certain amount of compressionover the epoxy joint to ensure the joint is properly set. This processis repeated until all deck units 21 are installed.

The deck end anchor unit 28 is made composite to the supporting girder15 by grouting the shear connector pocket 22 and haunch 17. Suchcomposite action is preferably made early since the deck jacking can'tbe applied before the grout reaches the required strength. After alldeck units are erected, jacking brackets 30 are installed. Jackingoperations consist of the following steps:

Install a jack 32 inside each jacking bracket 30;Shim all jacks 32 tightly against the jacking bracket end bearing plate36 and bearing plate for the deck jacking unit 38;Gradually increase the jacking load to the design value; andLock all jacks 32 to maintain the jacking force.

After the jacking operation, shear connector pockets and haunches aregrouted, except those occupied by jacking brackets 30. After the groutfor shear connector and haunch reaches the specified strength, jacks 32and jacking brackets 30 are released and removed, A secondary groutingwill then be conducted to fill in the remaining opening left by thejacking brackets 30.

The operational description above is particular to the preferredembodiment of the present invention in the context of a single spanbridge heretofore defined. Alternate materials, member shapes, number ofspans, means of jacking, means 290 of making composite action betweendeck and girder, etc. can be used in employing the structuralconstruction system of the present invention.

Advantages

The present invention provides a practical method to transfer jackingforces to longitudinal compression in the prefabricated deck units whenjacking the deck against the supporting girder. This significantlyreduces the cost and time of construction required.

CONCLUSION, RAMIFICATIONS, AND SCOPE

In conclusion, the present invention provides a jacking force transfermethod used in combination with prefabricated bridge deck units that issimple to implement. The present invention can accommodate a variety ofstructural configurations and can be rapidly deployed.

Although the description above contains many specificities, these shouldnot be construed as limiting the scope of the invention but as merelyproviding illustrations of some of the preferred embodiments of thisinvention at present. For example, as illustrated and described herein,the present invention can be employed a variety of bridge span layouts,a variety of girder types, and via a variety of means to make compositeaction between deck and girders.

Thus, the scope of the invention should be determined by the appendedclaims and their legal equivalents, rather than by the examples given.

I claim:
 1. A jacking force transfer system, whereby a jacking force orforces originating from a jack or jacks may be transferred to compressprefabricated units with support means disposed on an element orelements oriented primarily in the direction of said jacking force orforces, comprising: a. a load-carrying member or members, i. whereinsaid load-carrying member or members are subjected to the jacking forceor forces originating from a jack or jacks, ii. wherein saidload-carrying member or members have relative movement means disposedwith the prefabricated units, iii. wherein said load-carrying member ormembers are substantively oriented in the direction of the jacking forceor forces, whereby said load-carrying member or members are subjected toaxial and shear forces and bending moments, iv. wherein saidload-carrying member or members have affixment means disposed to theelement or elements in a direction oriented primarily perpendicular tothe direction of said jacking force or forces, v. wherein saidload-carrying member or members have contact means disposed to theelement or elements in a direction oriented primarily perpendicular tothe direction of said jacking force or forces, and vi. where saidaffixment means and said contact means are substantively offset from oneanother in a direction oriented primarily parallel to the direction ofsaid jacking force or forces, whereby two reactions result that act tostabilize said load-carrying members and act to resist overturningmoments resulting from said jacking force or forces, and b. aload-carrying member or members, i. wherein said load-carrying member ormembers have affixment means disposed to the element or elements, ii.wherein said load-carrying member or members have contact means disposedwith the load-carrying member or members of claim 1a, and iii. whereinsaid load-carrying member or members are offset in a direction orientedprimarily perpendicular to the direction of said jacking force, wherebysaid load-carrying member or members are subjected to substantivelyshear or compression forces.
 2. The jacking force transfer system claim1, wherein a unity or a plurality of the prefabricated units arecomposite with a unity or a plurality of the element or elements,whereby said unity or plurality of the prefabricated units are subjectedto the jacking force or forces.
 3. The jacking force transfer system ofclaim 1, wherein the element or elements are comprised of any one memberor any combination of members selected from the group consisting ofsteel, concrete, wood, and composite materials.
 4. The jacking forcetransfer system of claim 1, wherein the element or elements of claim 1are comprised of any one member or any combination of members selectedfrom the group consisting of I-girders, I-beams, box-girders, andbox-beams.
 5. The jacking force transfer system of claim 1, wherein theelement or elements of claim 1 are comprised of any one member or anycombination of members selected from the group consisting of bridgebeams, bridge girders, and bridge slabs.
 6. The jacking force transfersystem of claim 1, wherein the element or elements of claim 1 arecomprised of any one member or any combination of members selected fromthe group consisting of the same element or elements, contiguouselements, connected elements, and separate elements.
 7. The jackingforce transfer system of claim 1, wherein the prefabricated units arecomprised of any one member or any combination of members selected fromthe group consisting of steel, concrete, wood, and composite materials.8. The jacking force transfer system of claim 1, wherein theprefabricated units are comprised of any one member or any combinationof members selected from the group consisting of bridge deck panels,budding floor panels, and building roof panels.
 9. The jacking forcetransfer system of claim 1, wherein the support means of claim 1 arecomprised of any one member or any combination of members selected fromthe group consisting of shims, rollers, sliders, spacers, pre-formedfiller, blocks, bearing pads, forms, grit, grease, lubricant, directcontact, grout, concrete, and channels.
 10. The jacking force transfersystem of claim 1, wherein the relative movement means of claim 1a arecomprised of any one of any one member or any combination of membersselected from the group consisting of physical gap, block-outs, andpre-formed flexible filler.
 11. The jacking force transfer systemload-carrying member or members of claim 1, wherein the affixment meansof claim 1a are comprised of any one member or any combination ofmembers selected from the group consisting of post-tensioning rods, tierods, pipes, tubes, plates, cables, tendons, chains, nuts, welds,threads, fasteners, hooks, clevis, pins, and couplers.
 12. The jackingforce transfer system load-carrying member or members of claim 1,wherein the contact means of claim 1a are comprised of any one member orany combination of members selected from the group consisting of shims,plates, blocks, spacers, bearing pads, and direct contact.
 13. Thejacking force transfer system load-carrying member or members of claim1, wherein the load-carrying member or members of claim 1a are locatedsubstantively to one end of the element or elements.
 14. The jackingforce transfer system load-carrying member or members of claim 1,wherein the load-carrying member or members of claim 1b are comprised ofany one member or any combination of members selected from the groupconsisting of steel, concrete, wood, and composite materials.
 15. Thejacking force transfer system load-carrying member or members of claim1, wherein the load-carrying member or members of claim 1b are comprisedof any one member or any combination of members selected from the groupconsisting of plates, blocks, and channels.
 16. The jacking forcetransfer system of claim 1, wherein the affixment means of claim 1b arecomprised of any one of any one member or any combination of membersselected from the group consisting of nuts, welds, threads, andfasteners.
 17. The jacking force transfer system of claim 1, wherein thecontact means of claim 1b are comprised of any one of any one member orany combination of members selected from the group consisting of shims,plates, blocks, spacers, and bearing pads.